INTRODUCTION 13 



may be placed on a cover-slip in Hantsch's fluid or Amann's medium * 

 and protected from dust until the volatile constituents have evapo- 

 rated. A smaller cover-slip may then be placed over the specimen, 

 using a minute drop of glycerine jelly, and the whole inverted on a slide 

 over Canada balsam, using the method described by W. W. Diehl, 

 thus providing a permanent mount suitable for examination under oil 

 immersion; or the material may be mounted directly on a slide in 

 glycerine jelly, and ringed with any good microscopic cement. For 

 nearly all species the best mounts are those which are held in a satu- 

 rated atmosphere for a few hours and then mounted in water. When 

 care is taken that the spores of such specimens are not permitted to 

 swell, as they do previous to germination, they often afford the most 

 favorable mounts for the determination of spore markings. 



Careful comparison of spores from fructifications kept in a saturated 

 atmosphere and mounted in water, with those mounted in weak po- 

 tassium hydroxide shows that there is no appreciable difference be- 

 tween the measurements made of spores mounted in these two ways, 

 and since the KOH is much more rapid, it is ordinarily used. In the case 

 of some genera, e. g., Cribraria, Dictydium and many of the Trichiales, 

 the addition of the alkali produces a marked color change. This may 

 sometimes be avoided by substituting lactic acid. Many fructifications 

 contain large spore-like bodies, often somewhat irregular in shape, 

 which are the result of failure of the protoplasm to proceed to complete 

 division. In measuring spores, these bodies must be excluded. If the 

 spores are on the whole uniform in size, an average of ten measure- 

 ments may be taken as representative of the collection. Where the 

 spores are more variable, a larger number of measurements must be 

 made. 



In the matter of nomenclature, the attempt has been made to adhere 

 to the rules of the International Botanical Code. In certain instances, 

 where the rules permit some degree of latitude, the authors have pre- 

 ferred to err on the side of strictness rather than laxity. It is believed 

 that in the long run this will be more likely to lead to nomenclatorial 

 stabilization than the greater freedom permitted, but scarcely en- 

 couraged, by the rules. 



♦Hantsch's fluid: 



Alcohol 90% three parts 



Water two parts 



Glycerine ... . . . • • • . . one part 



Amann's medium: 



Phenol 20gms. 



Lactic acid .......... 20 gms. 



Glycerine 40 ml. 



Water 20ml. 



